Endocrine 7: calcium hemostasis int.

Question 1

Functions of Ionic calcium in the body (Ca2+)

Answer 1

Makes up 1% of total body calcium:
1. Blood clotting: activation of some factors
2. Secondary messenger: in cellular actions of some hormones
3. Membrane excitability
4. Muscle contraction
5. Cardiac function : maintains contractility & rhythmicity
6. Exocrine secretion, endocrine secretion & Neurosecretion

Question 2

Functions of Calcium salt

Answer 2

99% of total body calcium:
* constitution in tissues (bone and teeth)
* Storage function

Question 3

distribution of Calcium in bones

Answer 3

99% of total body clacium:
* Small Liable pool (readily exchangable with plasma calcium)
* Large fixed pool (unexchangable) as Calcium hydroxapatite

Question 4

Other sites of Rapid Calcium exchange with plasma calcium

Answer 4

• Liver
• Intestine

Question 5

average plasma Calcium conc.

Answer 5

10mg/dl

Question 6

Calcium in plasma is divided into:

Answer 6

• Diffusable form (53.6%)
• Non-diffusable (46.4%) bound to plasma proteins mainly albumin

Question 7

Site of absorption of most Calcium in GIT

Answer 7

Upper small intestine (duodenum)

by both passive diffusion & Active diffusion

Question 8

Describe factors affecting absoprtion of Calcium

Answer 8

Local:
* Acidity of duodenum (helps dissolve calcium)
* Protein meals (for soluble complex with calcium)
* Acidic food products (lactose or citrates)
* Phosphates & oxalates –> reduce solubility of Calcium

Vitamin D3

Question 9

Most of phosphorus in the body is present in:

Answer 9

Bones (85-90%)

Question 10

normal Plasma concentration of phosphorus

Answer 10

+- 12mg/dl

Question 11

precipitation of Calcium phosphate occurs if:

Answer 11

Physiologically: osteoblasts release inhibitor for pyrophosphate (allowing precepitation to form)

Pathologically:
* Metabolic calcification
* Subendothelial in atherosclerosis
* Degenerated cells

Question 12

Matrix of bone made up of:

Answer 12

Type 1 collagen

Question 13

Crystals of bone are mostly:

Answer 13

Calcium hydroxyapatite

Question 14

Mention cells of bone tissue & their function

Answer 14

Osteoblast (bone building):
* Secrete collagen
* Secretes alkaline phosphatase –> hydrolyses plasma phosphate into phosphate ions to form calcium phosphate
* Secrete pyrophosphate inhibitor, to allow pericipitation to occur

Osteoclast (bone eating cells):
* Secrete H+ ions that dissolves Hydroxapatite crystals
* Secrete acid protease to dissolve collagen

Osteocyts: responsible for Calcium exchange with ECF (by forming osteocytic membrane)